Pro Tips: How to Choose a Sleeping Bag
By Michael Lanza
Finding a sleeping bag that’s right for you may be the most confusing gear-buying task. Getting the right one is critical to sleeping comfortably in the backcountry, and your bag could save your life in an emergency. But with the myriad choices out there, how do you tell them apart, beyond temperature rating and price? I’ve slept in many, many bags as a gear tester for two decades (and counting) for Backpacker and this blog, in all seasons, in temperatures from very mild to -30° F. (Mild is more pleasant.) In this article, I’ll share what I’ve learned about picking out a sleeping bag that will be ideal for your body and your adventures.
General Tips For Buying a Sleeping Bag
• Know your own body. Do you get cold easily or are you a furnace? Women tend to get cold more easily, and this is a simple function of physics: Women often have a higher ratio of body surface area to mass compared to men, so their bodies lose heat more readily. Those women are more comfortable in a bag made for women, which is shaped differently than a men’s bag and typically has extra insulation in areas like the feet.
• If you get cold easily, get a bag rated 20 to 25 degrees colder than the coldest temperatures you plan to sleep outside in.
• People who don’t get cold easily will be more comfortable in a bag rated to within 10 to 15 degrees of the coldest temperatures you plan to sleep outside in—and possibly even a bag rated right around the coldest temp you’ll encounter, provided you have extra clothing to put on, just in case. (I’ve spent many nights around freezing perfectly warm enough in a bag rated 32° F.) Being too hot is no more comfortable than being too cold, and having a bag much warmer than needed means you’re carrying superfluous weight and bulk. (See my tips on lightening your pack weight.)
Down Vs. Synthetic Bags
Down has traditionally been lighter, more packable, and warmer than many synthetic insulations; but once wet, synthetics still kept you fairly warm, while down feathers become all but useless at retaining heat. Today, the lines between down and synthetic have been blurred somewhat with the development of high-quality, lightweight and compact synthetic insulations like PrimaLoft, and water-resistant down, which retains its ability to trap heat even when wet.
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Down is more packable and very durable, so it still holds an advantage as the insulation of choice if you don’t expect to get that bag wet; and water-resistant down enhances your bag’s performance in common circumstances where it may get damp, such as when condensation builds up inside a tent. Still, even water-resistant down, once saturated, loses much of its ability to keep you warm, and drying out any bag is extremely difficult, if not impossible, in prolonged, wet weather. Synthetic insulation remains the best choice for extended trips in wet environments.
High-quality down (generally rated from 700- to 850-fill) is the warmest, lightest, most packable insulation out there, but expensive, while lower-quality down (usually 600-fill) still has the advantages of down, and makes a bag less expensive but also heavier and bulkier. Manufacturers use lower-grade synthetic insulation in bags priced cheaply, making them much heavier and bulkier than better synthetic and down bags—typically too heavy and bulky for backpacking (unless you’re on a very limited budget and don’t mind carrying a big pack).
So the down vs. synthetic choice still comes down to pocketbook issues and the likelihood of your bag actually getting wet.
In the past, bag manufacturers decided on temperature ratings for their own bags; the outdoor industry lacked a standardized method for measuring that. In recent years, though, the industry widely adopted the EN (European Norm) temperature rating system, internationally considered the most reliable and objective standard.
Found on most new bags, the EN rating typically includes three temperature ratings:
• Comfort rating, or the lowest temperature at which the bag will keep the average woman warm (based on the premise that women usually get cold more easily than men).
• Lower-limit rating, or the lowest temperature at which the bag will keep the average man warm.
• Extreme rating, or the lowest temperature at which the bag will keep someone alive, albeit not comfortable, in unexpected, extreme conditions.
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Summer Sleeping Bags
• By “summer” sleeping bag, I mean a bag rated roughly 32° F or higher, for camping in temperatures that you don’t expect to drop below freezing—in other words, as low as the 30s, but more likely not lower than the 40s or 50s Fahrenheit. I don’t get cold easily, so I virtually always use a bag rated around 30° F for summer trips when I expect nights in the 30s to around 50° F. People who get cold easily may not want a 30° F bag except for temps above 50° F.
• Summer bags are designed for low weight and bulk, so some lack features of warmer bags, like a thick draft tube or collar, a full-length zipper, sometimes even a hood. You often don’t need those features in a summer bag—you can wear a hat or base layers when needed. Personally, I often prefer a hood on a summer bag, because you can adjust it more loosely than a hat fits your head, which I find more comfortable; but that’s a matter of preference.
Three-Season Sleeping Bags
• By “three-season” sleeping bag, I mean a bag rated roughly 10° to 32° F, for camping in temperatures that may range from the 20s to around 40° F.
• These bags have an adjustable hood and features like a draft tube, though they may still have a partial instead of a full-length zipper, to shave a few ounces.
• Many consumers consider bags in this category the one all-purpose bag they need, versatile enough for spring, summer, or fall. My advice: Choose a bag rating that’s suited to your body (how easily you get cold) and the typical lowest temps you will camp in, not according to a more vague definition of seasons.
Winter Sleeping Bags
• By “winter” bag, I mean a bag rated roughly 10° F or lower, for sleeping in temperatures below freezing—which could mean the teens or 20s or even below zero Fahrenheit.
• Someone who gets cold easily may want a bag rated for winter temperatures even when camping in temperatures that range from the 20s to around 40° F.
While the expected low temperatures and your own needs should dictate what temperature rating to look for, there are factors I consider specific to a winter bag that differ from the other three seasons:
• I like to have a little extra rolling-around space for a few reasons:
1. In case I’m wearing extra layers or packing extra clothing around my body for added insulation if temperatures drop lower than expected.
2. For stuffing damp layers inside my bag to dry them overnight, or to keep extra layers, camp booties, or liner boots warm for when I put them on come morning.
3. To have room to get dressed and undressed inside the bag, where it’s much warmer than inside my tent (my test: I like to be able to easily lift my knees to my chest while lying inside the bag).
4. Simply because I’m often going to close a winter bag up tight, and a too-snug bag can feel claustrophobic.
• In temperatures below freezing, condensation from your breath will make a bag wet, so it ideally remains unaffected by moisture through the use of either synthetic or water-resistant down insulation, or a shell fabric that’s water-resistant or waterproof and breathable.
• Lastly, I prefer a winter bag with high-quality down or synthetic insulation, to minimize its already substantial weight and bulk, but you pay extra for that.
The type of baffles used in a sleeping bag affects its warmth and price.
• Sewn-through baffles, the cheapest and lightest method of putting a bag together, create “cold spots” where the external and internal fabric are sewn together, leaving small gaps between pockets of insulation. This saves you money but should only be considered for the mildest nights.
• Vertical baffles run the length of the bag and typically have internal barriers to prevent down feathers from migrating and creating cold spots.
• Horizontal baffles are used in many high-end bags to maximize the warmth-to-weight ratio.
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Shape and Features
You can find various styles and shapes of sleeping bags for the backcountry these days:
• Traditional, “mummy” bags, which taper from head to foot, are still the most common, and it’s also most common for insulation to be spread throughout the bag so that the person is completely wrapped in insulation.
• The dimensions—or living space—of a bag matter, especially in a mummy bag, which is inherently more cramped than other styles (such as rectangular bags, a design common among inexpensive products made for car-camping and for kids).
• Because the insulation that you lie atop usually gets compressed, negating its insulating value, some companies, like Big Agnes, market bags with no insulation on the bottom, replaced by a full-length sleeve into which you slide a pad or air mattress, which doubles as the insulation on the bag’s uninsulated side. This style puts all of the insulation where it will actually help keep you warm. But side sleepers may not find these bags comfortable because they don’t roll with you.
• Zippers vary from full-length to partial-length, the latter style reducing a bag’s weight without greatly affecting the ease of entry and exit. Some bags have two-way zippers, allowing you to ventilate at the foot end as well as at the top.
• Quilt-style bags range from products very much like a basic quilt to newer models like the Sierra Designs Backcountry Bed, which marries features of quilts and traditional, hooded bags.
• Wearable sleeping bags have sealable arm ports, a foot end that opens and closes, and a way to roll or fold the foot end up so that it hangs on your body like a long, down coat, allowing you to wear the bag while walking around and to use your hands. This eliminates (or reduces) the weight of a puffy jacket from your pack. Two leading models are the Exped Dreamwalker 450 (read my review) and the Sierra Designs Mobile Mummy 800 (read my review).
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